Inhibitor for gasoline



Patented Feb. 9, 1943 ITOR ron GASOLINE Robert H. Rosenwald and JosephA. Chenicek, Re

Chicago, IlL, assignors to Universal Oil Prodnets Company, Chicago,111., a corporation of Delaware Reissued I 5, 39 June 6, 1950 NoDrawing. Application September 18, 1939, Serial No. 295,476

18 Claims.

This invention relates to a method for stabilizing olefin-containinghydrocarbon oils, and more particularly, cracked gasolines of thepetroleum origin. However, gasolines from other sources, such as coaltar, shale oil, etc., may be also treat ed according to the presentinvention, as may those made by polymerization of olefins, reforming ofnaphthas, etc.

More specifically, the invention concerns a method for stabilizingolefin-containing gasolines during storage in respect to their valuableproperties such as color and anti-knock value and low gum content whichtend to depreciate because of the action of oxygen upon theoleflns insaid gasolines.

The cracking and reforming processes which are employed to produceadditional yields of gasoline from heavy hydrocarbonaceous oils, or toincrease the antiknock properties of naphthas and straight-rungasolines, produce motor fuels having substantial concentrations ofunsaturated hydrocarbons, particularly mono-olefins and dicleflns. Theseolefinic hydrocarbons tend to form peroxides and gums when stored in thepresence of oxygen. The use of inhibitors to prevent such reactions hasbeen practiced, and many types of compounds have been suggested for thispurpose, including aminophenols, wood tar fractions, polyhydroxyphenols, etc.

In one specific embodiment, the present invention comprises thetreatment of unstable olefin-containing gasolines to preserve theirvaluable properties in respect to gum content, color and antiknock valueby adding thereto minor quantities of 2-alkyl-4-alkoxyphenols of thegeneral structure wherein R. comprises any alkyl group and OR is analkoxy group wherein R is of the same or different molecular weight andstructure than R.

The properties desirable in a gasoline gum inhibitor are as follows:

a. Solubility in the gasoline to a degree in excess of the maximumconcentration in which it is likely to be used.

h. High degree of potency so that relatively small concentrations can beused.

c. Insolubility or relatively low solubility in water or aqueousalkaline or acidic solutions with which the gasoline is likely to comein contact.

:1. Either normally liquid or having a high degree of solubility in anon-aqueous, gasolinemisci-ble solvent thus increasing the ease ofhandling and addition to the gasoline.

e. Non-reactive with tanks, fittings, lines, engine parts, etc., withwhich the gasoline is likely to come in contact.

j. Of light color, and imparting or developing no objectionable color orodor to the gasoline when added, or during storage.

The inhibitors of the present invention to a large extent fulfil theserequirements.

The degree of insolubility of an inhibitor in water or caustic solutionsis of particular importance since gasoline storage tanks generallycontain water which is alkaline in reaction. If the inhibitor is solublein the water layer, it is partially removed from the gasoline and thusits effect is greatly reduced. The present type of compound has beenfound to be practically in soluble in water and in slightly removablefrom gasoline by contact with dilute alkaline solutions.

The compounds of the present invention are useful for preventing thedeterioration of gasoline, but diiierent individual compounds of thesame type are not necessarily exact equivalents.

The alkyl groups substituted in the ring may comprise any alkyl groupsuch as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondarybutyl, t-butyl, amyl, isoamyl, secondary amyl, etc. Of these groups, thet-alkyl groups appear to 'be more efiective in contributing to theinhibitor potency of the resultant compound than do those groups oflower molecular weight, for example methyl and ethyl groups. Likewise,the groups of higher molecular weight contribute to other desirableproperties of the inhibitor such as decreasing the solubility of theresulting compound in aqueous solutions. The substituent group ispreferably in the position ortho to the hydroxyl group. Some compoundshaving alkyl groups in the meta position may also have inhibiting value.

We have found that when the alkoxy or ether group is in the -positlon,compounds having greater inhibitor potency are available than when thisgroup is in any other position in the substituted phenol. The alkylgroup of this alkoxy substituent may comprise for example ethyl, methyl,propyl, isopropyl, 'butyl, isobutyl, secondary butyl, t-butyl, amyl,isoamyl, secondary most cases to be but lows:

Hydroqulnone =0.00 Hydroquinone monoimothylethenfltil 110G015: mcoQonCzHs 1H5 2-othylhydroquinone=0.35 2 ethyl-4-mothoxyphenol=2.39

In this case, the inhibitor potencies of the various compounds listed asgiven by the numerical values, were measured by means of the oxygen bombinduction period test, and the inhibitor potencies are reported as"inhibitor ratio. The inhibitor ratio is defined as the ratio of theincrease in induction period of a given gasoline by a given percentageof unknown inhibitor to the induction period increase with a likequantity of a standard commercial gum inhibitor. Thus the' values asreported are direct ratios of inhibitor potency as compared with awidely used commercial gum inhibitor. From the illustration it will benoted that hydroquinone and ethylhydroquinone have little or noinhibitor value compared with the commercial inhibitor. The monomethylether of hydroquinone has a considerable potency, being 1.69 times asefiective as the commercial inhibitor. The substitution of an ethylgroup in the position ortho to the hydroxyl group(2-ethyl-4-methoxyphenol) increases the inhibitor ratio to an evengreater extent, so that the resulting 2-ethyl-4-methoxyphenol is 2.39times as effective as the commercial inhibitor.

The alkyl substituents may be introduced into the aromatic nucleus in anumber of ways. one of these consists in alkylating a hydroquinone etherby contacting it at a temperature 01' -80 C. with the alcoholcorresponding to the group to be substituted, using phosphoric acid asthe catalyst. The reaction mixture is stirred continuously until thereaction is complete. The mixture is then washed with water to removeremaining acid and is extracted with 10% sodium hydroxide solution toremove the unreacted hydroqulnone ether. The insoluble portion isdistilled under reduced pressure and the resulting compound may befurther purified by recrystallization.

The term stabilizing gasoline as used herein is intended to mean theprevention of deterioration of the gasoline in so far as its desirableproperties of storage stability, color, antilrnock value,

'etc., are concerned.

The following example still further illustrates the benefits andusefulness of the present type of inhibitor. This example is given todemonstrate the usefulness and practicability of our invention, butshould not be construed as limiting it to the exact compoundsillustrated therein. As in the foregoing, the inhibiting value in so faras the stabilization of gasoline is concerned is reported in terms ofinhibitor ratio compared with a commercially used gum inhibitor.

In the following table are shown a number of representative compounds ofthe present invention together with their inhibitor ratios:

TABLE I Inhibitor ratios of 2-aZkyl-4-alkozyphenols in 0.05%concentration Compound Structural iormnla ga? Commercial inhibitor 1.00

2-ethyl-4-methoxyphenol. HOQO CH; 2. 39

2-ethyl-4-eihoxyphen0l H090 01H. aaa

Z-allyl-i-mathoxyphenol HO-Q-O 03, 2.19

Hr- C H=C H:

2-propyl-4-mothoxyphenol HOQ-O CH: 2. 30

2-tert-butyl-i-methoxyphenol.. HOQO on. a. m

2-tert-butyl-4-athoxyphenol HOQO 01H} 4.40

2tert-butyl-t-lsopropoxyphenol.. HOQ o-omom). a as aeromo 3 CompoundStructural formula Inhibitor ratio fi-tert-butyl-i-isobutoxyphenol. HOQOCHr-CH (CH 2. 78

Z-t-amyl-i-mcthoxyphenol H0 0 CH 3.

t-CaHn The results show that the compounds listed are speciallyeffective inhibitors as compared to a commercial gum inhibitor when usedin equal weights. They are not, however, exactly equivalent since thespecific efiects of different groups in the alkoxy or in the ortho ringsubstituted positions may be quite different. Thus it will be seen thatan ethyl or methyl group in the alkom group is more efiective than otheralkyl groups tried. on the other hand, the substitution of a t-butylgroup in the aromatic ring greatly increases the inhibitor potency ofthe resultant compound.

The effectiveness is further illustrated by the quantities. In allcases, the color of the resulting gasoline was equal to or better thanthat of the gasoline inhibited with a commercial inhibitor.

It has been our observation in the laboratory that the inhibitors ofthis invention are comparatively stable insofar as color is concernedwhen exposed to air. One of the disadvantages of many commercialinhibitors is that they develop color rapidly when exposed to air. Thestable character of the present inhibitors may therefore be consideredan advantage.

We claim as our invention:

1. A process for stabilizing olefin-containing hydrocarbon oils inregard to their desirable data presented in Table II. properties whichcomprises adding to said oils TABLE II Oxygen bomb induction Per centremoved Mg dish gum .Pcriod by- Inhibitor Orig Water Caustic orl WaterCaustic Water Caustic wash wash wash wash wash Wash Blank gasoline 127138 184 90 80 75 Commercial inhibitor 4 24 180 310 260 100 18 89Z-tert-butyl-t-mcthoxyphenol- 8 7 9 305 310 295 0 02tert-butyl-4-ethoxyphcnol 7 9 10 310 336 330 0 02-tert-butyl-4-isogropoxyphenol 15 15 17 290 295 280 0 02-tert-butyl-4-iso utoxyphenol.-. 16 24 19 310 300 295 0 0Z-ethyl-i-mcthoxyphcnoL 37 64 19 300 300 145 0 67 2-ethyl-t-ethoxy 13.19 28 290 300 180 0 47 Hydroquinune monoethyl ether 32 38 104 310 280100 9 89 Hydroquinone mouo-isopropyl ether 27 44 115 280 270 90 0 92 thegasoline was inhibited with a sumcient quantity of each inhibitor toproduce apprommately the same induction period. Hydroquinonemonoethylether and monoiso-propylether are included in. the list forpurposes of comparison. The percentage of inhibitor removed by water orcaustic is calculated from the per cent decrease in induction periodafter the sample has been washed with water or with caustic solution. Itwill be noted that the compounds of the present invention are lesssoluble in water than the commercial inhibitor or hydroquinonemonoethylether. Moreover, these compounds are less soluble in dilutecaustic solution that the monoalkylethers or the commercial guminhibitor. It will be noted also that the t-butyl group as the ringsubstituent reduces the alkali solubility of the compounds to a greaterextent than does an ethyl group in the same position. It will also beobserved that the compounds of the present invention have practically nodetrimental efiect on the color or color stability of the gasoline whenadded in these a minor portion of a compound having the generalstructure wherein R and R comprise alkyl groups.

3. A process for stabilizing cracked gasoline against deterioration ofits valuable properties which comprises adding to said gasoline a minorportion of a compound of the following general formula:

wherein R is a t-allryl group and R is an allryl group.

i. A process for stabilizing olefin-containing gasoline againstdeterioration of its valuable properties which comprises adding to saidgasoline a minor portion of a compound of the following general formula:

wherein R and R are t-alkyl groups.

6. A process for stabilizing olefin-containing gasoline againstdeterioration of its valuable properties which comprises adding to saidgasoline a minor portion of a 2-alkyl-4-alkoxyphenol.

7. An inhibitor for cracked gasoline which comprises essentially acompound having the general formula:

wherein R and R are alkyl groups.

8. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula:

wherein R is an alkyl group and R is a difierent alkyl group.

aaiwrio a. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula on i l R R! wherein Rcomprises a t-allryl group and R an alkyl group.

10. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula on B R! wherein R is at-butyl and R is an alkyl group. 11. An inhibitor for olefin-containinggasoline which comprises essentially a compound having the generalformula on i R R! wherein R and R are t-alkyl groups.

12. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula on R R! wherein R isan alkyl group and R is a t-alkyl group.

13. An inhibitor for olefin-containing gasoline which comprisesessentially a compound having the general formula wherein R is a t-alkylgroup and R is a t-butyl group.

14. Motor fuel comprising oleflnic gasoline and a relatively smallamount of a 2-alkyl-4-alkoxyphenol.

15. Motor fuel comprising olefinic gasoline and a relatively smallamount of a 2-t-alkyl-4- alkoxyphenol.

16. Motor fuel comprising oleflnic gasoline and o, rollotively smallamount of a compound having 18. An inhibitor comprising a. compoundhavibho general formula, ing the general formula on on wherein R is analkyl group of at least 3 carbon 10 wherein R is an alkyl group of atleast 3 carbon atoms and R is an alkyl group of less than 3 atoms and Ris an alkyl group of less than 3 corbon atoms. carbon atoms.

17. inhibitor comprising a 2-a1ky1-4-a1koxy- ROBERT H. ROSENWALD.phenol. JOSEPH A. CHENICEK.

